The coilovers allow more adjustment believe it or not. With air bags to get a compression rate difference you must in flate or deflate the airbag, this in turn changes ride height. With a coil-over you have the option to change height and compression as well as rate independent of each other.
Now, in this comparison I'm speaking of conventional air-bag setups.
But, if you were to use limiting straps and stops, then some of that could be thrown out the window.
But with a coilover the you also still have options for different spring rates (1 rate, 2 rate, progressive/variable). With your air bag you will still be limited by the properties of air and its ability to be compressed.
Air-bags could be viable. I hope that if you chose to use them that it comes out without a glitch. On the other hand they could be a tuning nightmare, due to the extra fabrication and equipment required to accomodate certain changes.
In my application. I need a coil-over due to space constraints.
I wouldn't want to use a "Shockwave" for hardcore racing. So I would have to have the airbag and the shocks mounted separately. This would be a bit problematic for me.
For street driving and a little bit of play, I might run the "Shockwaves" but on ly then. I don't feel they would hold up very well to the abuse that my suspension must contend with. They're a bit pricey to replace on a regular basis.
I'm sure that I've forgatten something But, if I did; I imagine it will be mentioned.
~Wes~